A maintenance fitter was thrown through the windscreen of a wheeled excavator after he crashed it while not wearing a seat belt.

He was left in a coma for two weeks and is still recovering. His employer was prosecuted and was yesterday fined £12,500 and ordered to pay costs of £29,660.

The fitter was working for Nottinghamshire piling contractor Van Elle Ltd on the M1 widening between Junctions 25 and 28 in the East Midlands. On 22 January 2009 the boom of a wheeled excavator he was driving struck a bridge.

The man, who has asked not to be named, was thrown over the steering column and through the open front screen, hitting his head on the front excavator blade. He suffered severe head injuries and was in a coma for two weeks. Rehabilitation lasted a further five months and he has since returned to the company though he has been left with reduced function in his left arm and leg for which he still receives physiotherapy.

The Health & Safety Executive (HSE) investigation found the driver had not received adequate training in use of the excavator. He had been assessed to carry out lifting operations at the company's premises but on the day in question was standing in for a regular driver on the motorway construction site.

Mansfield magistrates heard how he was driving through the site with the excavator boom at a height of 6m – well above the manufacturer’s recommended 4m maximum.

After the hearing HSE inspector Kevin Wilson said: "This worker was extremely lucky to escape with his life. As it is he has been left with life-changing injuries.

"These injuries were wholly preventable had the company ensured the driver had adequate training in safe travel positions for manoeuvring the excavator on the construction project.

"They failed to take into account his lack of training for the particular task; there was a risk of striking overhead restrictions from when the journey started with the boom in the elevated position. His injuries could have been mitigated against if the operator had been wearing his seatbelt."

Van Elle Ltd, of Kirkby Lane, Pinxton, Nottinghamshire, pleaded guilty to breaching Regulation 9(1) of the Provision and Use of Work Equipment Regulations 1998.